In many deposition chambers, both atomic layer deposition and chemical vapor deposition, rotating pedestal/heaters are used to improve non-uniformity. In most cases, non-uniformity comes from non-uniform chemical delivery, flow distribution, chamber features, and temperature non-uniformity from the chamber body and surrounding components. Using a rotating pedestal can distribute the local effect of these variations and improve the non-uniformity.
However, in some cases, non-uniformity can be contributed by the pedestal or the heater itself, especially when the substrate (wafer) sits on or contacts the heater. The impact of local non-uniform temperature distribution can have a significant impact on the uniformity of deposition. This non-uniform temperature distribution can come from heater element layout, local features like lift pin holes, non-uniform radiative heat loss, non-uniform contact surface or gap, or other reasons.
It is increasingly necessary to rotate a heater/pedestal to get the best film uniformity during Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) processes where heated pedestal is used. A typical issue with rotating pedestal designs is that the rotating assembly becomes very complex. Installing or removing the pedestal requires disconnecting vacuum feeds, electrical feeds and resistance temperature detectors (RTD). Typical RTD sensor assemblies for monitoring temperature are designed such that the RTD sensor is located at the tip of the assembly and the other end has connecting/signal wires which connects to an RTD converter box. This RTD assembly is then inserted inside the pedestal after it is installed in the chamber from the bottom. However, with the rotating mechanism disposed below the chamber, it makes it difficult for one to install or remove the RTD assembly without damaging the part. There is also a considerable amount of time required to install/remove the RTD assembly.
Therefore, there is a need in the art for apparatus and methods to improve heater and RTD assembly installation and removal for rotating heater pedestals.